Lower extremity amputation (LEA) is a very severe and catastrophic complication of diabetes mellitus. According to the Centers for Disease Control in 2005, per hospital discharge the overall rate of LEA is 4.3 per 1,000 persons with diabetes as compared to about 3 per 10,000 per year the rest of our population. Annually more than 50% of all non-traumatic amputations occur in patients with diabetes, thereby making diabetes the leading cause of lower extremity non-traumatic amputation. Because a foot ulcer is often the single most important reason that an individual eventually has an LEA, effective treatment for foot ulcer is essential for the prevention of LEA. It was estimated in 2004 that $9.7 billion dollars in direct medical costs were allocated to the treatment of wounds. Care now can include the use of treatment adjuvant to standard therapy called hyperbaric oxygen. In 2005, at a Medicare Coverage Advisory meeting on wound care, it was noted that the likelihood that large randomized clinical trials evaluating the efficacy of adjuvant agents would be conducted was deemed very doubtful. Unfortunately, large cohort studies have also not been conducted to determine the effectiveness of this device. The ultimate goals of this application are to better understand the comparative effectiveness of hyperbaric oxygen therapy when we have previously studied chronic wounds of the lower extremity using medical records/administrative data from community-based wound care centers. We plan to investigate this issue using an instrumental variable approach, effective and cost-effectiveness study designs, and database from National Healing Corporation, which is one of the largest wound community-based wound management companies in the United States.